link impairments a few - ucsb€¦ · oscillator am and pm sidebands (skip): cosinusoidal phase...

Copyright Mark Rodwell, 2016

Link Impairments

A few

Mark Rodwell, University of California, Santa Barbara

ece145c lecture notes


Reminder: Multipath Propagation

n"propagatiopath -multi" :paths signalMany

pattern. beam antennain objectsMany

antennas)y directivit-(lowbeamwidth angular largeGiven

reflection ofStrenght

antennas ofy Directivit

strenght signaldifferent haspath Each

shift. phase possible :conditionboundary surface Reflecting

delay.different length,different haspath Each


Fading vs Intersymbol interference

periods symbollonger :ODFM useor

receiverin equalizer adapitive need

another with interfers periodbit One

ceinterferen lIntersymboperiod) Symbol spread(Delay

separation eappropriatat antennas receiving two:fix

signalery weak possibly vceinterferenphase ofout are Carriers

aligned~ periods symbol with arrive signals NLOS and LOS

Fadingperiod) Symbol spread(Delay


Interference by Intermodulation (1)

ce.interferen cause also will tonesdistortion These

. )2( and )2( sfrequencieat tonesdistortion

generate will and sfrequencieat signalsinput strong

, *distortionorder -odd*Given

1221

21

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signal. desired with theinterfere willand passband,filter IF e within thliemay

)2(or )2(either yet passband,filter IF theoutside sfrequencie to

d translatebemay ) , ( tonesginterferin original themixer, After the

mixer. and stage RF

by the produced be will)2( and )2(at then tones

passband, filter the RF e within thlie and at tones theIf

ce.interferen nosuffer illreceiver w theand rejected, be they will

filter, RF theof passband theoutside lie and at tones theIf

1221

21

1221

21

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it. outside lie es themselevsignals ginterferin even the passband,

sfilter' baseband e within thliemay productsation intermodul The

occur.may ation intermodul strong that stages IF

in the isit case, in this gain;high very have amplifiers IF The

filters. IF *and*

RF both the of passbands theinside liemay and at

sinterferer strong thereceiver, conversion-dual aIn

21 ff


Interference by LO Phase Noise

y.sensitivitreceiver thedegrade willThis

overlap. willsignals variousof spectra converted-down The

spectrum. oscillator thebroadens This

ns.fluctuatio timinghave sOscillator Real


Oscillator phase modulation

)exp()()exp(

))(1)(exp()(

(radian) 1)( :ionapproximat angle-Small

))(exp()exp()(

)()( nsfluctuatio phase have We

))(exp()exp(

))((exp()(

:)( nsfluctuatio timingAdd

)exp()(

:nOscillatio

0,0,

0,

0,

0,

0,

0,

tjVtjtjV

tjtjVtV

t

tjtjVtV

tTt

tTjtjV

tTtjVtV

tT

tjVtV

LOLOLOLOLO

LOLOLOLO

LO

LOLOLOLO

LOLO

LOLOLO

LOLOLO

LOLOLO


Oscillator phase modulation

))(exp()2/())(exp()2/(

)exp( )(

)exp()exp()2/(

)exp()exp()2/()exp( )(

Then

)exp()2/()exp()2/()cos()(

:assume Now

)exp()()exp( )(

:nOscillatio

0,0,

0,

0,

0,0,

0,0,

tjVjtjVj

tjVtV

tjVtjj

tjVtjjtjVtV

tjtjtt

tjVtjtjVtV

mLOLOcmLOLOc

LOLOLO

LOLOmc

LOLOmcLOLOLO

mcmcmcLO

LOLOLOLOLOLO

deviation phase Squared-Mean2powercarrier

power sideband total

2/ :amplitude Sideband

:at Sidebands

2

c

c

mLO

j


Oscillator phase: sinusoidal modulation

))(exp()2/())(exp()2/(

)exp( )(

Then

)exp()2/()exp()2/()sin()(

:assume Instead

)exp()()exp( )(

:nsfluctuatio phasen with Oscillatio

0,0,

0,

0,0,

tjVjtjVj

tjVtV

tjjtjjtt

tjVtjtjVtV

mLOLOSmLOLOS

LOLOLO

mSmSmSLO

LOLOLOLOLOLO


power sideband total

2/ :amplitudes Sideband

:at Sidebands

2

S

S

mLO


Oscillator AM and PM sidebands (skip)

.modulation phase sinusoidal : .modulation phase alcosinusoid :

.modulation amplitude sinusoidal : .modulation amplitude alcosinusoid :

))sincos(exp()sincos1()( :Signal /

sc

sc

msmcLOmsmcpmam

NN

tttjtNtNtv

2/2/sideband modulation phase

2/2/sideband modulation amplitude

where

:sidebandlower :sidebandupper

)()()(2)(

:SpectrumFourier

**

CSp

sca

paupau

mLOumLOuLO

jC

jNNC

CCCCCC

CCjV


Oscillator AM and PM sidebands (skip)

PMn larger tha bemight AM :sources Optical

AM PMusually :soscillatortor in transis /clippingSaturation

sidebands. PM and AM ofconsist sidebands Total


Oscillator phase noise

)() (4)()()(

) () (2)(

) (

) (2)(2

1)exp()(

) ()exp(

:ansformsFourier tr

)()()(density spectral random, is )( :Assume

)exp()()exp( )(

:nsfluctuatio phasen with Oscillatio

2*

0,

*

0,0,

LOLOLOLOVV

LOLOLOLO

LOLO

LOLOLOLOLO

LOLO

LOLOLO

LOLOLOLOLOLO

SjVjVjS

jjV

djtjVtF

tjF

jjjSt

tjVtjtjVtV

)() (2)(

correctjust will.Isomewhere.error 2 a up picked veI'

LOLOVV SjS


Oscillator phase noise

)() (2

)() (2)(

LOLO

LOLOVV

L

SjS

)( sidebands plus line,n oscillatio central

:oscillator of spectrumPower

)( : nsfluctuatio phase of spectrumPower

LOS

S


power sideband total 2

S

offset 100Hzat

radians/Hz 10 of magnitude a has means

" dBc(1Hz)100)Hz100("

bandwidth 1Hz ain carrier torelative dB as )(

as expressedusually noise Phase

1/25-

S

fL

fL


Signal interference from LO phase noise

ysensitivitreceiver thedegradegreatly willand , above 43dB is This

dBm(1Hz)130dBc(1Hz)10030dBm

dBc(1Hz)100)MHz1( power, received 30dBm , from MHz 1offset

:Example

(dB/Hz) )(dB)(

unitslinear )(

:at density SpectralPower Noise Equivalent

referred-input ifeasiest are nsCalculatio

signals.both tosidebands add willnoise phase LO IF, At the

power frequency :signal gInterferin

power frequency :signal Received

1

11

11

11

kT

S

Lff

ffLP

ffLPS

f

Pf

Pf

noise

RF

RF

RFnoise

RF

rfRF


Constellation rotation from phase noise

ionconstellat in the

pointsdecision themove also will

corrected,not if

phase, LO theof nsFluctuatio

impairment iscorrect th also

can processing digital ADC-Post

ns.fluctuatio phase se track theattempt to

willPLL LOreceiver The


Error Vector Magnitude

ysensitivitreceiver reduced

decreased thereby is SNR effective The

.boundariesdecision thecloser to

vectorsignal themove willeffects theseAll

link impairments a few - ucsb€¦ · oscillator am and pm sidebands (skip): cosinusoidal phase...

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